1. Field of the Invention
The present invention relates to diamond cutting tools, and more particularly to diamond cutting tools such as a diamond core drill and a disk-shaped diamond saw which are used to grind and cut hard articles in order to bore concrete walls to repair concrete buildings etc., or cut hard articles such as testing samples and metallic workpiece, and which are improved in structures of diamond blade portions, which are made by pressing and heating metal and diamond powders, positioned at outer edge of the diamond cutting tools so as to improve machinability and lengthen working life of the cutting tools.
2. Description of the Prior Art
Referring to FIG. 1A, there is shown a known diamond core drill. The diamond core drill comprises a cup-shaped tool body 10A, an annular diamond blade portion 20A fixedly attached to the upper circumferential edge of the cup-shaped tool body 10A, and a shaft 11 formed the center of lower surface of the cup-shaped tool body 10A which is to be coupled to a power transmission shaft (not shown).
The annular diamond blade portion 20A is formed at an upper half part thereof with a plurality of cuts 21A which are circumferentially spaced from each other at certain intervals. Therefore, the cuts 21A formed at the diamond blade portion 20A cause chips from workpieces to be discharged therethrough and prevent slippage of the diamond blade portion 20A on workpieces, thereby improving machinability of the diamond core drill.
However, since the diamond core drill has the cuts 21A which are formed to only about middle depth of the annular diamond blade portion 20A in order to prevent failure thereof due to friction with workpieces of hard material, the diamond blade portion 20A has a flat cutting surface after the annular diamond blade portion 20A has worn away to a depth corresponding to the bottom of the cuts 21A. Therefore, machinability of the diamond core drill is remarkably decreased after the diamond blade portion 20A is worn away to the bottom of the cuts 21A, thereby causing working life thereof to be shortened.
On the other hand, referring to FIG. 1B, there is shown a known disk-shaped diamond saw. The disk-shaped diamond saw comprises a disk 10B and an annular diamond blade portion 20B attached to the outer circumferential edge of the disk 10B. As similar to the diamond core tool shown in FIG. 1A, the diamond saw is provided at the circumferential margin thereof with a plurality of radial slits 21B. The slits 21B are circumferentially spaced from each other at certain intervals each of which extends into the disk 10B from the periphery of the diamond blade portion 20B.
The diamond saw has somewhat machinability as result of being formed with the slits 21B. However, the slits 21B are not intended to improve machinability of the diamond saw but mainly intended to provide to the diamond saw with strength and elasticity to resist bending moment vertical to the surface of diamond saw during cutting work. In addition, the diamond saw is constructed such that the slits 21B are spaced from each other at large intervals so that the diamond blade portion 20B slips on workpieces during cutting work, thereby causing its machinability to be decreased.